Patient Indications

Indications for arthroscopic surgery vary between joints. In the elbow joint, most common indications include fragmented medial coronoid process (FCP), osteochondritis dissecans (OCD) of the elbow, and ununited anconeal process. Less common indications may include biopsies of the joint capsule in cases of immune-mediated arthritis or capsular neoplasia, evaluation of fractures of the condyle, or reduction of elbow fractures and debridement of the joint in cases of septic arthritis. In the shoulder the most common indications include OCD of the humeral head, biceps tendon tenosynovitis, and evaluation of medial shoulder instability. Less common indications may include capsular biopsy, evaluation of glenoid fractures, or debridement in cases of septic arthritis. In the stifle, the most common indications include stifle OCD, meniscectomy, or debridement of the CCL stumps in dogs with CCL rupture. Less common indications include evaluation of fractures of the condyle or patella or debridement of septic joints. The tarsus, carpus, and hip joints are much less commonly scoped. The hip may be evaluated arthroscopically to assess cartilage condition and integrity before triple pelvic osteotomy. The tarsus can be evaluated for OCD lesions, and these may be removed with the use of an arthroscopic approach. The carpus (radiocarpal joint) is rarely scoped but can be debrided or evaluated in cases of undiagnosed lameness involving this joint.

Patient Contraindications

There are few contraindications specifically for arthroscopic surgery. Perhaps the most common contraindication would be animals or joints that are simply too small to allow examination. When a 1.9-mm arthroscope is used, dogs as small as 12- to 13-kg body weight may be scoped, but instrumentation of joints in very small dogs and cats may be difficult or impossible. Dogs with severe arthritis and poor joint range of motion may present a challenge to the arthroscopist, but these severely degenerative joints are not a contraindication. Besides small size of the animal, the only other contraindications would be general ones that apply to any surgery, such as animals being poor anesthetic candidates or having severe systemic diseases rendering their joint problems irrelevant.

Equipment for Small Animal Arthroscopy

Arthroscopy in the dog requires high-quality equipment that can be obtained from several manufacturers. It is ill advised to purchase outdated, used equipment because the technology has changed so much in recent years. The following discussion will give the budding arthroscopist advice on what equipment is needed to perform quality arthroscopic procedures. High-quality equipment is not a substitute for practice and attention to detail when learning arthroscopic skills, but poor quality equipment will frustrate and hamper progression of one’s skills.

Arthroscopes

The initial instrument that is considered is the arthroscope itself. Arthroscopes are surgical telescopes that allow visualization of the joint. These scopes are rigid tubes with lenses on the ends and fiberoptic bundles in the tube that allow transmission of the image and light. Arthroscopes are available in several diameters including 4.0, 2.7, 2.4, and 1.9 mm (Figure 21-1). The most commonly used endoscope in small animal orthopedics is the 2.7-mm arthroscope. The 2.4-mm scope is very similar, and the 1.9-mm scope is useful in smaller joints such as the carpus or tarsus. The 4.0-mm scope is too large for most dogs and is rarely used in companion animals. In addition to varying diameters, several lengths and viewing angles are available for arthroscopes. Most veterinary arthroscopists use a shorter scope (12 cm or less in length), although scopes are available up to 18 cm. Viewing angles of 0, 30, and 70 degrees have been used in the past, but the 30-degree arthroscope is almost exclusively used by veterinary arthroscopists. Even though arthroscopes have an eyepiece for direct viewing, all modern arthroscopy is performed with the use of a video arthroscope. The final feature of all arthroscopes is a post for attaching the light cable.

Figure 21-1 Commonly used arthroscopes for small animal surgery include the 2.7-, 2.4-, and 1.9-mm arthroscopes.

(Photo courtesy of Karl Storz GmbH & Co. KG, Tuttlingen, Germany.)

Because arthroscopes are rigid stainless steel tubes containing fiberoptics, a few words regarding care of the instrument are in order. Arthroscopes are fragile and do not tolerate bending or being dropped. An arthroscope should always be kept in its protective sheath or in its cannula. Arthroscopy should never be performed without a scope cannula. Visualization of the joint is made possible by carefully locating portals, not by forcing the scope into an inaccessible area. Using an arthroscope as a crowbar to force a view into the joint can break the scope, resulting in an unwarranted expense. Sterilization of the arthroscope is by ethylene oxide (ETO), by soaking in glutaraldehyde solution, or by plasma sterilization. Soaking in glutaraldehyde is messy and can be irritating to mucous membranes for most people. Certain scopes can be autoclaved, but this process will decrease the life of the scope.

Video Camera and Control Unit, Light Sources, and Monitor

All veterinary arthroscopy is performed with the use of a video camera. These cameras attach to the arthroscope by several mechanisms that vary by manufacturer. Video cameras may be single chip or three chip, and all give an excellent picture with good resolution. The three-chip camera is preferred by most arthroscopists because it allows higher quality pictures and video to be recorded. In addition, most camera heads have two to three buttons that can be programmed to perform a number of functions, including taking still pictures or video, controlling the light intensity, or turning on and off digital enhancement software. The camera head is sterilized by ETO, soaking in glutaraldehyde solution, or by plasma sterilization.

Light sources are an important part of the arthroscopy tower. Both halogen and xenon light sources have been used, but xenon is almost exclusively used in arthroscopy. The light cable is sterilized by ETO, by soaking in glutaraldehyde, or by plasma sterilization.

The monitor is the screen that is used to visualize the joint. Most modern monitors are high-definition flat screen monitors that give excellent picture quality. Monitor size varies considerably, but the rule of thumb is to purchase the largest monitor that fits your arthroscopy cart and your budget. A 21-inch or larger monitor is ideal because it allows the arthroscopy cart to be backed away from the surgical table as much as possible. The operating table area gets very crowded with all of the equipment necessary to perform the procedure, and the farther the arthroscopy cart is from the table, the more room is left for the surgeon and assistant to work.

Video Capture Equipment

When arthroscopic surgery is performed, it is not necessary to have equipment to take photographs or video images of the procedure, but it is nevertheless useful. One use of this equipment is to record images for teaching purposes. It is also helpful to record images for the medical record so that arthroscopic lesions can be correlated with surgical outcomes. One of the most important reasons to record images of the procedures is for marketing. Most clients and referring veterinarians enjoy having pictures of the procedures, and it makes explaining the procedure to the client much easier.

Fluid Management

During arthroscopic surgery, fluid continually flows through the joint to provide a clear field of view, free of blood and debris. For fluid to flow, an ingress and egress portal must be established in all joints. The route of ingress and egress varies from procedure to procedure and will be discussed later in this chapter. It is important to control both the flow and the pressure within the joint so that the joint is kept distended and fluid extravasation outside the joint is minimized. If the pressure within the joint is too low, the joint collapses and the surgeon is unable to see structures within the joint. If the pressure is too high, the fluid flows out of the joint into the subcutaneous area, leading to joint collapse and poor visualization. Fluid management is very important during the procedure, and there are three main ways that fluid flow and pressure are managed during surgery.

The simplest way to manage fluid within the joint is simply through gravity. The fluid irrigation bags are suspended from the operating room ceiling, and fluid is delivered imprecisely to the surgical site with the use of a standard intravenous infusion set. Pressure and flow are controlled by raising and lowering the bags. Many surgeons use this technique because it is inexpensive and effective; however, control of flow and pressure is limited, and optimal joint distension may not be achieved.

A variation of this technique is to use the inflatable fluid delivery devices designed to deliver fluid under pressure intravenously to trauma patients. The fluid bag is inserted into the inflatable device, and a hand pump is used to pressurize the system, delivering fluids at a varying pressure. These devices work well for arthroscopy, but one needs to be very careful not to overinflate the bag because too high a pressure leads to serious fluid extravasation and joint collapse.

The ideal way to deliver fluid to the joint is to use a mechanical arthroscopy pump (Figure 21-2). Several manufacturers market these pumps, and most use either an impeller or a roller pump to control fluid flow rate. A transducer built into the fluid line is used to precisely control pressure within the joint. The pumps work well, and fluid extravasation is minimized through optimal fluid management. For most arthroscopic procedures, a high flow setting is used with a modest pressure. Typically, pressures within the joint are set at 25 to 40 mm Hg. If bleeding from the joint capsule is a problem or the joint is not distending well, higher pressures can be used but rarely exceed 60 mm Hg. When choosing an arthroscopy pump to purchase, one should investigate the cost of the pump along with the cost of the tubing to determine whether the tubing can be used on more than one case or can be resterilized. Single-use tubing that cannot be reused may be prohibitively expensive.

Figure 21-2 Typical arthroscopic fluid pump.

(Photo courtesy of Karl Storz GmbH & Co. KG, Tuttlingen, Germany.)

Shavers

A power shaver is an important part of any arthroscopy setup (Figure 21-3). The power shaver is a motorized power tool that allows the rapid and precise removal of bone, cartilage, and soft tissue. The essential components of most power shaver units are the electronic control box, a handpiece and bit, and the foot pedal. The power shaver may be controlled with the use of a hand control or a foot control, but most surgeons prefer a foot control. The control box contains the electrical apparatus and controls for revolutions per minute of the handpiece. The handpiece is the motor and couples to interchangeable bits for different jobs, and the foot pedal is a variable speed controller that also allows the bit to rotate forward or backward or to oscillate. The speed of the handpiece is generally set to 1500 to 2500 rpm for most small animal procedures. Bits are cannulated so that debris that is cut is immediately removed from the joint by surgical suction that is coupled to the handpiece. Bits are a tube within a tube in which the inner tube rotates. The outer tube is a tissue guard that serves to protect the soft tissue. There is a defect on the side or end of the outer tube that exposes the blade or burr that does the cutting. Many types of bits are available, but the most useful for small animal arthroscopy are aggressive cutting blades that are 2.5 to 4.0 mm in diameter. Burr bits are also helpful and can be obtained in the same size range.

Figure 21-3 Arthroscopic power shaver and handpiece.

(Photo courtesy of Karl Storz GmbH & Co. KG, Tuttlingen, Germany.)

Cannulas, Trocars, and Obturators

Cannulas are hollow stainless steel tubes that are used to introduce both the arthroscope and some instruments into the joint. There are several types of cannulas, and their purpose is to maintain the portal (incision into the joint); protect the scope, instruments, and soft tissue; and serve as a way to introduce or remove irrigation fluid from the joint. Scope cannulas are matched to the size of the arthroscope and are generally about 2 mm larger in diameter than the scope. Instrument cannulas are optional for use and come in many diameters. Some instruments do not fit through a cannula well, and sometimes instrument cannulas actually interfere with movement of the instrument within the joint. Irrigation cannulas are similar to the scope cannula in diameter and have ports on the sides as well as an open end. Irrigation cannulas can be used for fluid ingress or egress, depending on the situation.

Trocars and obturators fit into the cannulas and are used to introduce the cannula into the joint. Trocars are very sharp and can cause significant cartilage damage; therefore, they should be used with caution. Obturators may be conical or blunt and do not have as much potential for damaging cartilage. The trocar or obturator is removed as soon as the joint capsule is penetrated and is not used again unless the cannula is removed from the joint and requires reinsertion.

Hand Instruments

There are literally hundreds of arthroscopic hand instruments available, and many of them are very expensive. The veterinary surgeon should select wisely from this wide variety of hand instruments and only purchase those that will be used commonly. There are only a few hand instruments that are needed to perform arthroscopic surgery in dogs, and these will be described individually.

The first hand instrument necessary is a probe (Figure 21-4). This is a straight stainless steel rod with a 90-degree bend at the end so that it forms a small hook. This instrument is used to manipulate pieces of bone and cartilage, retract soft tissue, and check the integrity of articular tissues. A small probe is best, and perhaps the most useful is a temporomandibular joint (TMJ) probe designed for use in the TMJ of humans. It is a nice size probe and easily fits through a 2.9-mm cannula. Some probes have alternating color bands so that the surgeon can get an idea of dimension when exploring joints or measuring lesions.